1. Field
The following description relates to an optical modulation device, a driving method thereof, and an optical device using the same. More particularly, the present invention relates to an optical modulation device using liquid crystal, a driving method thereof, and an optical device using the same.
2. Description of the Related Art
Recently, optical devices (e.g., display devices) using an optical modulation device for modulating an optical characteristic of the optical devices have been widely developed. For example, optical display devices for displaying three-dimensional (3D) images have been paid much attention, and they can include and/or use an optical modulation device to separate images and transmit the same at different times so that a viewer may recognize them as stereoscopic images. The optical modulation device is designed to be used in a stereoscopic image display device without using other viewing equipment, such as a lens and a prism, to change a path of light (e.g., images) displayed by a display device and transmit the same at a desired time.
Diffraction of light by phase modulation can be used to change a direction of incident light.
When polarized light passes through an optical modulation device, such as a phase delay unit, its polarized state is changed. For example, when circularly polarized light is input to a half-wave plate, a rotation direction of the circularly polarized light is changed to be opposite (e.g., 180° different) and the light is output. For example, when light circularly polarized to the left passes through the half-wave plate, light circularly polarized to the right is output. In this example, a phase of the circularly polarized output light is different depending on an optical axis of the half-wave plate, that is, an angle of a slow axis. For example, when an optical axis of the half-wave plate is rotated by in-plane φ, a phase of the output light is changed by 2φ. Therefore, when the optical axis of the half-wave plate is rotated by 180 degrees (π radian) in a spatially x-axis direction, the light can be output with phase modulation or phase change of 360 degrees (2π radian) in the x-axis direction. When the optical modulation changes the phase of inputted light from 0 to 2π according to positions on the optical modulation device, a diffraction lattice or a prism for changing or redirecting the direction of the passed light can be realized.
Liquid crystal can be used to easily control the optical axis of the optical modulation device, such as the half-wave plate, according to the position on the optical modulation device. Regarding the optical modulation device realized as a phase delay unit including liquid crystal, different phase modulations can be performed by rotating a long axis of liquid crystal molecules that are arranged according to an electric field applied to a liquid crystal layer. The phase of light that passes through the optical modulation device and is output can be determined (e.g., adjusted or varied) by the direction of the arranged liquid crystal molecules, that is, an azimuthal angle.
To perform consecutive phase modulations by using the optical modulation device using liquid crystal and a prism, a diffraction lattice, or a lens, the liquid crystal molecules must be arranged so that a long axis of the liquid crystal molecules may be consecutively changed according to the position on the optical modulation device. In order for the output light to have a phase profile that changes or varies from 0 to 2π according to the position, the optical axis of the half-wave plate must change or vary from 0 to π. For this purpose, a substrate that is adjacent to the liquid crystal layer may require alignments in different directions such the process becomes complicated. When the alignment must be finely distinguished and processed, it is difficult to uniformly perform the alignment process, such as a rubbing process, which may cause display faults when used in the display device.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.